In case where, in an information processing system in a data center or the like, plural virtual machines and the like for plural tenants (i.e. customers) are activated and operated on plural physical machines, there is a case where a desired throughput cannot be obtained when there is a lack of balance in the load in a network that connects the physical machines.
For example, an information processing system as illustrated in FIG. 1 is assumed. The information processing system in FIG. 1 includes three upper switches SSwitch1 to 3, three lower switches LSwitch1 to 3, physical machines AServer1 and 3 on which Virtual routers 1 and 2 are executed and physical machines VServer1 to 6 on which virtual machines VM1 to VM6 are executed.
In the example of FIG. 1, VM1 communicates with VM3 through LSwitch1, SSwitch1, Virtual router1, SSwitch1 and LSwitch2, and VM2 communicates with VM4 through LSwitch1, SSwitch1 and LSwitch2. Furthermore, VM5 communicates with VM6 through LSwitch2, SSwitch3, Virtual router2, SSwicth3 and LSwitch3.
In such a case, when focusing on LSwitch1, the output traffic of a link to SSwitch1 is “5”, however, the output traffic of a link to SSwitch2 and SSwitch3 is “0”. Because the output traffic of the link to SSwitch1 is greater, the latency may become high.
Then, in a conventional technique, a network controller that is connected to SSwitch1 may cooperate with the upper switches and lower switches to individually change communication paths between VMs. For example, a communication path between VM2 and VM4 is changed from a connection path that passes through LSwitch1, SSwitch1 and LSwitch2 to a communication path that passes through LSwitch1, SSwitch2 and LSwitch2, as illustrated in FIG. 2. Because, by this change, the output traffic of a link from LSwitch1 to SSwitch2 increases to “3”, the output traffic of a link from LSwitch1 to SSwitch1 is reduced to “2”.
Thus, there is a case where the output traffic can be equalized by individually changing the communication paths between VMs as described above.
However, such a method does not function in a next case. As illustrated in FIG. 3, the output traffic to Virtual router2 and the output traffic to Virtual router3 coincide on a link from SSwitch3 to a physical machine AServer3, however, it is impossible to avoid the coincidence of the output traffic even if the communication paths between the upper switch and the lower switch are changed in any patterns.
Similarly, as illustrated in FIG. 4, there is no substitute link with the link between LSwitch and VServer. Therefore, it is impossible to avoid a case where the latency becomes high when the output traffic of LSWitch1 from VM3 to VM2 via LSwitch1 and the output traffic of LSwitch1 from VM4 to VM1 through LSwitch1 coincide.
Patent Document 1: Japanese Laid-open Patent Publication No. 2012-94119
Patent Document 2: Japanese National Publication of International Patent Application No. 2012-511292